I have this old coin which is made in to a medallion. I was trying to find it on the Internet, checked a lot of websites, but I could not find the exact same coin. The front is the same as the front of 1917 Mercury Dime, but I was not able to find the same back. Another strange thing is that this coin does not have an year printed on it. I believe that either the coin is fake or it is a printing mistake, I don't know. I hope you will be able to help me with that. Below you can find images of the coin.

Thank you in advance!